Translaminar Full-Endoscopic Discectomy for Highly Migrated Disc Herniations

Article information

J Minim Invasive Spine Surg Tech. 2025;10(1):76-82

Publication date (electronic) : 2025 April 30

doi : https://doi.org/10.21182/jmisst.2025.02068

Arun Bhanot^,1, Meenakshi Arora², Ankush Garg¹

¹C K Birla Hospital, Gurugram, Haryana, India

²SGT University, Budhera, Gurugram, Haryana, India

Corresponding Author: Arun Bhanot C K Birla Hospital, H-7/10, Vatika India Next, Sector 82, Gurugram, Haryana, India Email: arunbhanot@gmail.com

Received 2025 January 21; Revised 2025 February 6; Accepted 2025 February 7.

Abstract

INTRODUCTION

Migrated disc herniation is defined as a herniation that has come out of the original disc space and either migrated superiorly or inferiorly beyond the borders of the end plates of the vertebrae of that motion segment. As per various reports, incidence of migrated disc herniation can vary from 35%–70% [1,2]. Lee et al. [3] classified these herniations and their severity based on the distance of migration of the herniated fragments (Figure 1, Table 1). The watershed line for recognizing highly migrated herniations was taken as the lower border of superior pedicle (Figure 1, Line A) and lower border of inferior pedicle (Figure 1, Line B) of the concerned motion segment.

Figure 1.

Graphic representation of disc migration classification.

Table 1.

Radiologic classification of migrated disc herniations [3]

However, in clinical practice, one often encounters disc herniations that go upwards even up to the upper border of superior pedicle and similarly beyond the inferior border of the inferior pedicle of lower vertebrae i.e., beyond zone 1 and zone 4. As such, herniations lying in zone 1 and 4 have been described as highly migrated herniations by Lee et al. [3,4] and found difficult to treat using a transforaminal endoscopic technique, leaving a high possibility of residual disc herniation. This is all the more true for herniations that are migrated beyond the superior border of superior pedicle and inferior border of inferior pedicle. Other alternative to transforaminal endoscopic removal of such discs is inter laminar full-endoscopic discectomy [5]. However, due to the nature of these migrated herniations, if one attempts to do an inter laminar endoscopy, there is a need for significant bony resection along with removal of the whole of ligamentum flavum, for better visualization and safe removal of the herniated disc fragments. Translaminar full-endoscopic discectomy can come quite handy in the management of such high migrated herniations with a least invasive approach and least bony resection [6-8]. In translaminar full-endoscopic discectomy (TFED), the working cannula is docked directly over the concerned lamina under which the migrated disc fragments lie. A bony tunnel/hole is then drilled through that lamina under direct endoscopic vision to expose the epidural space, neural structures and disc herniation. After securing hemostasis and good visualization, the migrated herniation is removed through the working channel endoscope. In this technique, there is hardly any need to remove the barrier of ligamentum flavum, as the working cannula and endoscope are targeted directly over the herniated fragments that are lying under the bony lamina. Translaminar approach has earlier been conceived to be used for removing migrated herniations using a microscope but it is less effective due to limited visualization provided by microscope [9-11]. Recently, there is a good interest in using the working channel endoscope to remove migrated disc herniations via the translaminar approach [6-8]. But most of the work on this subject has been focused on up migrated herniations, with one paper describing this technique’s usage for downmigrated herniation, to the best of our knowledge [12]. In this paper, we share our experience of using this least invasive technique using the working channel endoscope via the translaminar approach to remove the difficult high migrated herniations that are either superiorly or inferiorly migrated.

METHODS

This is a retrospective study of 10 patients who underwent TFED for severely migrated herniations at our spine unit between 2019–2023. There were 8 patients who underwent this surgery for upmigrated herniations and 2 patients for downmigrated herniations. The extent of herniation was either zone 1 or zone 4 and even beyond in both directions for all the patients. None of our patients were having zone 2 or 3 migrations as per Lee’s classification. The patient data in terms of demographics, level of herniation, direction of migration along with type of surgery chosen is presented in Table 2. All patients underwent high quality preoperative magnetic resonance imaging (MRI) scans. Computed tomography (CT) scans were done wherever the treating team deemed it suitable to check for calcified disc or bony window dimensions. Patients were evaluated for pain via visual analogue scale and Oswestry Disability Index preoperatively and postoperatively at 1-month, 3-month, 6-month, 1-year, and 2-year follow-up. Follow-up period ranged from 10–58 months with an average of 24.7 months.

Table 2.

Patient demographic data for this series of patients undergoing translaminar disc excision

Some patients were included for this study even in the presence of associated moderate stenosis especially if the new symptoms associated with recent disc herniation were the main presenting and dominant symptoms. However, when the stenosis symptoms were equally disturbing, such patients were excluded from this study and offered different treatment options. 2 out of 10 patients had associated radiological lumbar stenosis without obvious symptoms attributed to the stenosis at the time of clinical presentation. All patients underwent postoperative MRI either the same day or one day after the surgery and a few patients underwent postoperative CT scan to document the bony window created for performing the translaminar surgery.

SURGICAL TECHNIQUE

TFED is done under general anesthesia with the patient lying in prone position. Proper preoperative evaluation is done to localize the migrated disc fragments and their relationship to the surrounding bony structures. Adequacy of width of the lamina to be drilled is ascertained to avoid violating the pars interarticularis. We do not use any needle insertion technique prior to introduction of the working cannula. The surgery follows the similar pattern of inter laminar endoscopic surgery steps. We use an 8 mm working cannula with 4.1-mm working channel endoscope (Vertebris Interlaminar Endoscope, RIWO Spine, Knittlingen, Germany). An 8-mm stab incision is given directly over the concerned lamina to be drilled (superior lamina in case of upmigrated herniation and inferior lamina for downmigrated herniation). The blunt obturator is introduced under C-arm fluoroscopy and docked to touch the posterior surface of the lamina. Then the 8-mm beveled working cannula is introduced over the blunt obturator under fluoroscopic control. Once the cannula is positioned, the obturator is withdrawn and working channel endoscope is introduced. After careful dissection of the overlying muscle and soft tissue using mechanical forceps and radio frequency ablation, the posterior surface of the lamina is exposed. Medial boundary of lamina where it joins the spinous process is identified. Similarly, the lateral edge of the lamina till the border of pars interarticularis is identified under endoscopic visualization. This step is important to limit the amount of bony drilling to avoid violating the pars. Once the posterior cortical bone of lamina is cleared and well visualized, bony drilling is commenced, initially using a match stick type cutting burr under endoscopic vision. As the bone gets drilled, one encounters the change from ivory white cortical bone to spongy, bleeding cancellous bone. As drilling continues further anteriorly, the anterior cortex of the lamina gets exposed that again presents ivory white consistency. At this junction, the fine diamond drill is used to carefully drill the last part of the bony tunnel so that any inadvertent damage to the epidural structures is avoided. Once a small opening is created in the lamina, then one can either continue using the diamond drill or use a side protection endoscopic drill to widen the size of the trans laminar hole. The drilled hole can also be widened using endoscopic Kerrison punch. Usually, the drilled hole measures 6–8 mm in size, depending upon the location and size of migrated herniation. Once the desired hole is created in the lamina, one can visualize the lateral surface of the dural sac and the herniated disc fragments lying in the axilla of the exiting nerve root (for up migrated herniation). For downmigrated herniations, the disc fragments can be seen either in the axilla or shoulder of the traversing nerve root, depending upon nature of pathology. Sometimes, one has to shrink the epidural fat and epidural veins using radio frequency probe to have better visualization of anatomical structures. We do not advance the working cannula through the drilled hole and instead keep it docked on the bony margins of the trans laminar hole. This avoids creating unwanted increase in epidural pressure especially in the light of the fact that epidural space has already been compromised by the presence of large herniated disc fragments. The endoscope can be advanced further anteriorly, if needed, to have a closer look at the anatomical structures and see under the neural elements or around them for better inspection. Once the disc fragments are visualized, endoscopic hook/dissector is used to mobilize the fragments and remove them by using endoscopic grasping forces. If more than one fragment is suspected (which is usually the case in migrated herniations), then one has to swipe the right-angle nerve hook or bendable hook beneath the neural elements under careful visualization by rotating the endoscope. This maneuver helps to mobilize the remaining loose disc fragments and remove them as completely as possible. Once all the disc fragments are removed, one can advance the endoscope further inside the epidural space to look around for completion of discectomy. Hemostasis is secured at the end of the procedure and endoscope withdrawn and the surgical wound closed with a single skin suture. The aim of this technique is to focus on removal of the migrated, sequestered disc fragments only. One does not attempt to remove any central disc bulge or any disc bulge at the level of the intervertebral disc as part of preoperative surgical plan.

RESULTS

Out of the total of 10 patients, 5 were females and 5 were males. The mean age of the patients was 57.1 years (range, 36–76 years). The mean follow-up was 24.7 months (range, 10–36. months). The mean operative time was 93.4 minutes. Blood loss is not easy to quantify in full-endoscopic surgeries due to constant open saline irrigation method and this being a retrospective study, postoperative hemogram was also not available to evaluate the blood loss. All our patients showed highly migrated herniations either in zone I or IV or even beyond the superior or inferior borders of the respective pedicles. Eight patients were upmigrated disc herniations and 2 were downmigrated herniations. The clinical outcomes were significantly improved after the surgical intervention. All patients experienced significant relief from their preoperative radicular pain in the early postoperative period (preoperative visual analogue scale [VAS] score 8.8, postoperative VAS score 1.2). Mean preoperative Oswestry Disability Index (ODI) was 76.43% and mean postoperative ODI was 17.33%. Neurological deficit patients started showing early signs of neurological recovery that ranged from as early as 48 hours. Ninety percent of our patients showed excellent to good outcomes as per modified MacNab criteria. One patient had a fair outcome at the latest follow-up of 2 years. This patient had pre-existing lumbar stenosis besides the freshly presented sequestered disc herniation. No untoward intraoperative or perioperative complications were noted in any of the patients. Two patients experienced postoperative dysesthesia that lasted for 3 and 6 weeks and eventually settled.

Postoperative MRI and CT imaging showed complete removal of the herniated disc fragments in all but 1 patient. The 1 patient where a small residual disc herniation was noted, also went on to have an excellent clinical outcome subsequently. None of the cases showed violations of the boundary of pars interarticularis as seen on postoperative CT scan/x-ray.

1. Case Examples

Case 1. Downmigrated L3–4 large herniation (Figure 2).

Figure 2.

(A–C) A large right paracentral downmigrated herniation in zone 4, represented by the arrow in panel C. (D, E) Postoperative magnetic resonance imaging showing complete removal through a right translaminar window.

Case 2. L3–4 upmigrated, sequestered disc herniation (Figure 3).

Figure 3.

(A, B) Left paracentral upmigrated disc herniation going up to the L3 pedicle on the left side. (C, D) Intraoperative C-arm view showing the position of the cannula for translaminar endoscopy. (E–H) Postoperative magnetic resonance imaging and computed tomography scan showing adequate decompression and translaminar bony window, represented by blue arrows on computed tomography scan.

DISCUSSION

Translaminar endoscopic approach was first mentioned as a concept to remove migrated disc herniations in the foraminal/extraforaminal zone by Di Lorenzo et al. [9]. They drilled a hole at the lateral edge of pars interarticularis to access the foraminal herniation. Later Papavero et al. [10], Schulz et al. [11] and Soldner et al. [13] described the microscopic translaminar technique to remove migrated herniations. However, using the microscope posed a handicap of suboptimal visualization from a distance and need for extra manipulation of the neural structures under the available magnification and visualization. In addition, one could not easily look under the neural elements to search for multiple fragments, that is usually the hallmark of such migrated disc herniations. Translaminar endoscopic technique to remove such migrated herniations has a definite edge over other techniques due to the use of an angled working channel endoscope [6-8]. Translaminar discectomy using the tubular retractor has been reported with good outcomes to manage herniated discs encroaching the exiting nerve root in the preforaminal and foraminal zones [14,15]. TFED surgical technique has been described by various authors in the recent past using slightly different methods. Kim described using a larger stenosis endoscope with a 10-mm working cannula to begin with and then switching over to a 8-mm working cannula, deploying a smaller caliber endoscope [6,8]. They recommended to advance the working cannula into the epidural space to mobilize the herniated disc fragments as well as to retract the neural tissue. Raorane et al. [7] described a technique similar to ours using a smaller caliber endoscope throughout the procedure and only advancing the endoscope into the epidural space, keeping the working cannula docked over the edge of the hole drilled in bony lamina. However, they recommended using flexible forceps to fish out hidden fragments from under the neural elements to complete the discectomy. In our technique, we aim to remove the easily identifiable disc fragments from the axilla of the exiting nerve root first, while keeping the working cannula and endoscope outside the epidural space. Then, we advance the endoscope further anteriorly into the epidural space and rotate it in various directions to visually inspect any remaining loose disc fragments. In addition, we use an articulated blunt hook to swipe under the neural elements to mobilize these hidden loose disc fragments and bring them into the direct line of the endoscope for further removal. This ensures that there is no inadvertent grasping of any important neural or vascular structures while fishing out for hidden fragments. The advancement of endoscope into the epidural space ensures that every surgical maneuver is being done under clear magnified visualization.

Migrated sequestered disc herniations have been removed using full-endoscopic techniques earlier by using transforaminal approach as well as other improvisations like transpedicular approach and inter laminar approach [2-5]. However, inter laminar approach has a shortcoming of removing a lot of laminar bone to extract the migrated disc fragments. On the other hand, transforaminal approach requires the endoscope to be kept in an epidural location to remove the migrated disc fragments, which may not be able to remove all the fragments especially in high migrated varieties [3,4]. Similarly, a transpedicular approach will also have the limitation of removing only fragments lying in front of the pedicle as the bony tunnel drilled in the pedicle will put a constraint on the free movement of the endoscope inside the epidural space.

Some authors have also proposed to do 2 adjacent level foraminoplasty to access these highly migrated disc herniations for a successful removal [16]. The core philosophy of any minimally invasive technique should ensure the least collateral damage to normal structures while removing the pathology of disc herniation as completely as safely possible. On these criteria, a translaminar endoscopic approach seems to score above all other options as it utilizes a hole drilled in the bony lamina to remove the migrated disc herniation. Using a working channel endoscope for this purpose ensures that there is least muscle damage while targeting the working cannula directly over the migrated disc herniation. Secondly, the hole drilled in the bony lamina, is likely to get closed with new bone formation over the next few months thus ensuring no long-term physical disruption in the spinal anatomy. Translaminar endoscopic approach has been shown to be an effective approach to successfully treat highly migrated disc herniations. Most of the published work on these subject talks about upward migrated herniations with a few mentions of this technique for downmigrated herniations. Our work here shows the use of this technique in both types of migrated herniations with equal efficiency in a single study. But one has to remember that translaminar endoscopic technique is most suitable when the migrated disc herniation has sequestered and got separated from its parent disc. If there is an associated disc herniation at the level of the disc, this approach may not be suitable for a complete removal of the disc herniation.

There are some shortcomings in our work as well. Our patient data consists of a small series of 10 patients that precludes deriving any statistically significant conclusions. A longer follow-up with CT scan images would throw more information about the actual fate of the drilled hole in the lamina. A randomized controlled trial comparing other techniques will be the best way forward to truly assess the benefits of this technique over others.

CONCLUSION

Highly migrated disc herniations though uncommon, still pose a significant challenge to treat surgically. They usually occur in elderly populations and are multi fragmented many a times. Conventional approaches like inter laminar endoscopic technique require much more resection of bony lamina to access and remove these herniations. On the other hand, transforaminal approach may not ensure complete removal of the herniated fragments and leave residual disc behind. A translaminar endoscopic approach bridges the gap between the 2 approaches to successfully remove these herniations while ensuring least damage to the bony stabilizers.

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